System and methodology for running casing strings through a conductor tube

ABSTRACT

A technique facilitates miming of casing strings in a multilateral well. A conductor tube may be placed into a hole formed in a seabed. A plurality of oriented casings is deployed in the conductor tube and the oriented casings have a specific exit angle and azimuthal orientation. The orientation of each oriented casing is used to direct a corresponding drilling of a borehole and placement of a casing in the borehole in a manner which does not interfere with other boreholes and casings.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present document is based on and claims priority to U.S. ProvisionalApplication Ser. No. 61/863,163, filed Aug. 7, 2013, which isincorporated herein by reference in its entirety.

BACKGROUND

Hydrocarbon fluids such as oil and natural gas are obtained from asubterranean geologic formation, referred to as a reservoir, by drillinga well that penetrates the hydrocarbon-bearing formation. Once awellbore is drilled, various forms of well completion components may beinstalled to control and enhance efficiency of producing the variousfluids from the reservoir. One piece of equipment which may be installedis a casing which may be deployed in a corresponding, drilled borehole.In multilateral wells, multiple casings may be run in theircorresponding boreholes. The boreholes and casings are oriented to avoidinterfering with each other.

SUMMARY

In general, a methodology and system are provided for facilitatingrunning of casing strings in, for example, a multilateral well or systemof wells. A conductor tube may be placed into a hole formed in a seabed.A plurality of oriented casings is deployed in the conductor tube andthe oriented casings are arranged with a specific exit angle andazimuthal orientation. The orientation of each oriented casing is usedto direct a corresponding drilling of a borehole and placement of acasing in the borehole in a manner which does not interfere with otherboreholes and casings.

However, many modifications are possible without materially departingfrom the teachings of this disclosure. Accordingly, such modificationsare intended to be included within the scope of this disclosure asdefined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the disclosure will hereafter be described withreference to the accompanying drawings, wherein like reference numeralsdenote like elements. It should be understood, however, that theaccompanying figures illustrate the various implementations describedherein and are not meant to limit the scope of various technologiesdescribed herein, and:

FIG. 1 is a schematic illustration of an example of a platform used incooperation with a plurality of conductor tubes for constructing amultilateral well, according to an embodiment of the disclosure;

FIG. 2 is a schematic illustration of an example of a conductor tubehaving internal oriented casings, according to an embodiment of thedisclosure;

FIG. 3 is a schematic illustration of an example of a portion of anorientation system for orienting a plurality of oriented casings in aconductor tube, according to an embodiment of the disclosure;

FIG. 4 is an illustration of an example of a conductor tube extendinginto a well bay of a well platform, according to an embodiment of thedisclosure;

FIG. 5 is an illustration of an example of a module used in forming aconductor tube with internal oriented casings, according to anembodiment of the disclosure;

FIG. 6 is a cross-sectional illustration of the module illustrated inFIG. 5, according to an embodiment of the disclosure;

FIG. 7 is a cross-sectional view of a module having dual orientedcasings, according to an embodiment of the disclosure;

FIG. 8 is an illustration of an example of a centralizer plate having analignment pin which may be employed to align sequential modules,according to an embodiment of the disclosure;

FIG. 9 is an illustration of an example of an alignment hole forreceiving an alignment pin to align sequential modules, according to anembodiment of the disclosure;

FIG. 10 is an illustration of an example of sequential alignment pins ofsequential modules to ensure a desired orientation of the internaloriented casings, according to an embodiment of the disclosure;

FIG. 11 is an illustration of an example of a conductor tube installedin a hole in a seabed, according to an embodiment of the disclosure;

FIG. 12 is an illustration of an enlarged portion of the conductor tubeillustrating check valves disposed in the internal oriented casings,according to an embodiment of the disclosure;

FIG. 13 is an illustration of sequential modules of oriented casingsbeing assembled in a desired alignment, according to an embodiment ofthe disclosure; and

FIG. 14 is an illustration of a multilateral well in which a pluralityof lateral boreholes and corresponding casings have been properlyoriented in a non-interfering arrangement, according to an embodiment ofthe disclosure.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of some embodiments of the present disclosure. However,it will be understood by those of ordinary skill in the art that thesystem and/or methodology may be practiced without these details andthat numerous variations or modifications from the described embodimentsmay be possible.

The present disclosure generally relates to a system and methodology forfacilitating running of casing strings in, for example, a multilateralwell or system of multilateral wells. A conductor tube may be placedinto a hole formed in a seabed. A plurality of oriented casings isarranged in the conductor tube and the oriented casings have a specificexit angle and azimuthal orientation. In some embodiments, the systemand methodology facilitate running of dual casing strings from a dualwellhead and through a conductor tube to achieve specific exit anglesand azimuthal orientations. The orientation of each oriented casing isused to direct a corresponding drilling of a borehole and placement of acasing in the borehole in a manner which does not interfere with otherboreholes and casings. The orientation enables use of a plurality of theconductor tubes in cooperation with a platform by controlling theorientation of the multiple boreholes and casings of the multilateralwell.

In a specific example, a platform escape strategy is established byorienting dual casing strings from dual wellheads located along aplatform. The technique enables the dual casing strings associated witheach dual wellhead to be oriented and guided using prefabricatedconductor hardware. The prefabricated conductor hardware, e.g. conductortube related modules, provides control over the specific exit angle andazimuthal orientation of oriented pairs of casings disposed incorresponding conductor tubes which extend down to a seabed.

Referring generally to FIG. 1, an embodiment of a multilateral wellsystem 20 is illustrated. In this embodiment, the well system 20comprises a platform 22 having a plurality of platform slots 24 forcorresponding wellheads 26. Each wellhead 26 may correspond with alateral wellbore or a plurality of lateral wellbores accessed throughoriented casings 28. In some applications, the wellheads 26 may comprisedual wellheads which each correspond with a pair of oriented casings 28extending to lateral boreholes formed at a subsea location. In a varietyof applications, the platform 22 may comprise a gravity based structureconstructed for use in hydrocarbon production operations at suitableoffshore locations.

In the example illustrated, numerous wellheads 26 are associated withthe platform 22, and the oriented casings 28 corresponding with eachwellhead 26 are oriented to avoid interference with other boreholesdrilled into the subsea formation and lined with borehole casings. Eachgroup, e.g. pair, of oriented casings 28 associated with a correspondingwellhead 26 is oriented with a specific exit angle and azimuthalorientation so as to avoid interference with the boreholes and boreholecasings from other oriented casings 28 associated with othercorresponding wellheads 26. The number and arrangement of platform slots24 in a given platform 22 may vary depending on the application and maycomprise, for example, 10 to 30 slots. In the specific exampleillustrated, platform 22 comprises 20 slots which each have a dualwellhead to create a multilateral well having, for example, 40 lateralboreholes. It should be noted, however, that the system and methodologydescribed herein for orienting boreholes can be used both with multiplewellheads or with a single grouping of oriented casings associated witha single wellhead 26.

Referring generally to FIG. 2, an example of a structure 30 fororienting boreholes 32 of lateral wells is illustrated. In this example,a conductor tube 34 extends down from platform 22 and into a hole 36which may be drilled or otherwise formed in a seabed 38. In manyapplications, the conductor tube 34 is positioned in the hole 36 in agenerally vertical orientation and extends upwardly to platform 22. Aplurality of the oriented casings 28 is arranged within the conductortube 34 such that the oriented casings 28 are positioned in a desiredorientation. For example, the oriented casings 28 may be arranged sothat lower, outlet ends 40 of the oriented casings 28 have specific exitangles and a desired azimuthal orientation, as illustrated in FIG. 3.The specific exit angles and azimuthal orientations are predetermined sothat the boreholes 32 formed beneath the oriented casings 28 areproperly oriented to avoid interference with other boreholes of themultilateral well 20.

Depending on the application, a variety of orientation mechanisms 42 maybe employed to orient the casings 28 and the corresponding outlet ends40 with the specific, desired exit angles and azimuthal orientations.For example, various orientation mechanisms 42 may be constructed tosecure the oriented casings 28 in a desired relationship and to affixthe oriented casings 28 within the surrounding conductor tube 34 at theappropriate orientation. As discussed in greater detail below, theplurality of oriented casings 28 may be assembled in sequentiallyoriented and coupled modules to ensure that the oriented casings 28 andtheir corresponding lower outlet ends 40 are properly oriented for eachwellhead 26.

Once the oriented casings 28 and the corresponding conductor tube 34 areproperly oriented and placed in hole 36, boreholes 32 may be drilled.The drilling of boreholes 32 is at least initiated along a desiredtrajectory due to the exit angle and azimuthal orientation of theoriented casings 28 through which the drill string is routed. Afterdrilling the boreholes 32, appropriate borehole casings 44 may bedelivered down through oriented casings 28 and disposed in thecorresponding boreholes 32. The borehole casings 44 may be cemented inplace within their corresponding boreholes 32.

Referring generally to FIG. 4, a specific embodiment is illustrated inwhich the conductor tube 34 extends down into hole 36 from a well bay 46of platform 22. In this example, the conductor tube 34 is orientedgenerally vertically between the well bay 46 and the seabed 38.Additionally, this example illustrates the plurality of oriented casings28 as comprising two oriented casings 28 positioned within conductortube 34 and connected with wellhead 26 in the form of a dual wellhead.Depending on the application, the lengths, diameters, and configurationsof the various system components may vary. In a specific example usingstandard pipe diameters, the hole 36 may be drilled as a 42 inch holeand the conductor tube 34 may comprise a 36 inch diameter conductorpipe. In this example, the oriented casings 28 may comprise 16 inchdiameter casings and the borehole casings may comprise 13 and ⅜ inchborehole casings. However, other applications may use conductor tubesranging from 20 to 50 inches in diameter with oriented casings rangingfrom 6 to 24 inches in diameter that cooperate with borehole casingsfrom 4 to 22 inches in diameter. Additionally, it should be noted thatmany other diameters and sizes may be used depending on the parametersof a given application.

In some applications, the oriented casings 28 may be assembled viamodules 48 which are sequentially aligned to position the orientedcasings 28 so as to extend along a desired orientation and to providethe desired exit angle and azimuthal orientation. An example of module48 is illustrated in FIGS. 5-7 and comprises a pair of the orientedcasings 28 positioned in the surrounding conductor tube 34. Each module48 may comprise a section of the conductor tube 34 with correspondingsections of the oriented casings 28 such that the sections of conductortube 34 and corresponding sections of oriented casings 28 are stacked orcoupled together in a specific sequence that provides the desiredorientation of the internal oriented casings 28. However, the modules 48also may be formed as sections of oriented casings 28 which are stackedwithin a corresponding conductor tube 34. Additionally, the modules 48may be formed as sections of oriented casings 28 located incorresponding tubing sections which are then positioned and orientedwithin the surrounding conductor tube 34. Other configurations ofmodules 48 also may be used to provide the desired orientation oforiented casings 28 for a given application.

In the example illustrated, each module 48 comprises sections of theoriented casings 28 held within a corresponding section of the conductortube 34 at a desired location with a plurality of plates or centralizers50. The plates or centralizers 50 may be welded or otherwise connectedalong an interior of the conductor tube 34 so as to provide the desiredorientation of casings 28 for a given module 48. The sequential modules48 may be connected together by welding, friction fits, sealed insertionfits, threaded couplers, and/or by other suitable fasteners and/orfastening techniques. Sequential modules 48 are oriented with respect toeach other via suitable orientation features 52 which, in someapplications, are coupled with the centralizers 50 located at thelongitudinal ends of the module 48. Each module 48 also may be markedwith an identifier 54, such as a number or other indicator, whichensures that the appropriate module 48 is joined with the appropriatenext sequential module 48 so as to ensure the desired orientation oforiented casings 28 along the entire conductor tube 34.

As further illustrated in FIGS. 8 and 9, an example of orientationfeatures 52 comprises an orientation pin 56 (see FIG. 8) and acorresponding orientation opening or hole 58 (see FIG. 9). In thisexample, the orientation pin 56 extends from one of the centralizers 50located at a longitudinal end of one module 48 and is received by acorresponding orientation hole 58 located at a correspondinglongitudinal end of the next sequential module 48. The orientation pin56 and orientation hole 58 ensure that the oriented casings 28 ofsequential modules 48 are properly aligned once the orientation pin 56is inserted into the corresponding orientation hole 58. As furtherillustrated, the centralizers 50 also may be constructed with openings60 sized for receipt of oriented casings 28.

In some applications, the sequential modules 48 are constructed togradually rotate the orientation of the plurality, e.g. pair, oforiented casings 28 along the conductor tube 34. This gradual rotationof the orientation is illustrated schematically in FIG. 10 which showsthe differing angular positions of the pin 56 and openings 60 from onemodule 48 to the next. The overall alignment of oriented casings 28 andthe desired exit angle and azimuthal orientation at lower outlet ends 40may be achieved by coupling the appropriate modules 48 according totheir indicators 54.

Referring generally to FIGS. 11 and 12, an embodiment of the conductortube 34 and internal oriented casings 28 is illustrated. In thisembodiment, sequential modules 48 are coupled together sequentially asillustrated in FIG. 13. Additionally, the sequential modules 48 may beoriented via orientation pins 56 and corresponding orientation holes 58located at the ends of each module 48 to ensure proper engagement ofsequential modules once they are coupled together according to theidentifiers 54. In this example, a check valve 62 is located in eachoriented casing 28. For example, an individual check valve 62 may bepositioned proximate a lower end, e.g. proximate lower outlet end 40, ofeach oriented casing 28. The check valves 62 are oriented to allow downflow of fluid into the hole 36, as illustrated by arrows 64, whilerestricting or blocking up flow of fluid into the oriented casings 28.The check valves 62 are useful in cementing operations, e.g. cementingof hole 36, while blocking unwanted upflow of cement into the orientedcasings 28. It should be noted that in certain applications a checkvalve 62 may be omitted from one or more of the oriented casings 28. Forexample, one of the oriented casings 28 may be used for conducting theoutward flow of cement as indicated by arrows 64 without having a checkvalve 62. However, the other oriented casing or casings 28 comprise thecheck valve(s) 62 to restrict or block the up flow of cement into theother oriented casing or casings.

In an operational example, the hole 36 is initially drilled into theseabed 38 generally below the region of platform 22. The conductor tube34 is then dropped down into the hole 36. A plurality of orientedcasings 28, e.g. two oriented casings 28, is arranged and orientedwithin the conductor tube 34 (see FIG. 11). As discussed above, the pairof oriented casings 28 may be properly oriented within the correspondingconductor tube 34 during assembly of the conductor tube 34 and theinternal oriented casings 28 via sequential modules 48 (see FIG. 13).However, in other applications, the modules 48 may comprise internalmodules formed separately from the conductor tube 34 and comprisingsections of oriented casings 28 in combination with centralizers 50and/or a surrounding support tube. In this latter embodiment, theinternal modules 48 would be assembled and moved down through theconductor tube 34. In some applications, the modules 48 are formed withsections of conductor tube 34 and corresponding centralizers 50, and theoriented casings 28 are inserted down through openings 60 into conductortube 34 in a manner similar to inserting straws down into a tube.

After proper placement/arrangement of the oriented casings 28 withinconductor tube 34, a cementing operation may be performed by cementingdown through one of the oriented casings 28. The cement flows downthrough the check valve 62 (see FIGS. 11 and 12) of the oriented casing28 which is used for conducting the flow of cement (or down through anopen, oriented casing 28 if no check valve 62 is employed in theoriented casing 28 used to deliver the cement). However, the checkvalves 62 collectively block up flow of the cement into the otheroriented casing or casings 28. The cement flows down into hole 36 andfills the hole 36 up toward, to, or past the lower end of the conductortube 34 depending on the specifics of a given application.

Once this initial cementing operation is completed, the boreholes 32 maybe drilled. The drilling of each borehole 32 is initiated along aspecific predetermined exit angle and azimuthal orientation due to theorientation of the corresponding oriented casing 28. As described above,the oriented casings 28 in each conductor tube 34 are properly orientedto provide the specific, predetermined exit angle and azimuthalorientation. The exit angles and azimuthal orientations are enabled bythe appropriate construction and orientation of sections of the orientedcasings 28 via assembly of the proper sequence of modules 48 (or byusing other suitable orientation mechanisms 42). If check valves 62 areemployed, the check valves 62 may be removed by drilling through thecheck valves or by other suitable removal techniques. Following drillingof the boreholes 32, borehole casings 44 are placed along the boreholes32 and again are routed out of the corresponding oriented casings 28with the appropriate, predetermined exit angle and azimuthalorientation. After the borehole casings 44 are properly placed in thecorresponding boreholes 32, the borehole casings 44 may be cemented inplace by, for example, performing a cementing operation down through oneor more of the oriented casings 28.

If more than one conductor tube 34 is positioned, the oriented casings28 in each conductor tube 34 may be oriented collectively to provideunique exit angles and azimuthal orientations with respect to otheroriented casings 28 associated with other conductor tubes 34. Forexample, certain applications employ platform 22 with multiple platformslots 24, as illustrated in FIG. 1, to enable construction of amultilateral well. Each platform slot 24 is associated with thecorresponding wellhead 26, e.g. a corresponding dual wellhead, havingconductor tube 34 and internal oriented casings 28 extending below thecorresponding wellhead 26 to the appropriate hole 36 formed in seabed38.

The internal oriented casings 28 associated with each platform slot 24and corresponding wellhead 26 are uniquely oriented with respect to exitangle and azimuthal orientation with respect to the numerous otherinternal oriented casings 28. This enables the drilling of the multipleassociated boreholes 32 and placement of the multiple correspondingborehole casings 44 in a non-interfering pattern, as illustrated in FIG.14.

As described herein, the overall multilateral well system 20 maycomprise many types of systems and components for use in a variety ofsubterranean well applications. For example, various types of platforms22, platform slots 24, and wellheads 26 may be employed. The number andarrangement of platform slots 24 and wellheads 26 also may change fromone application to another. Additionally, the materials andconfigurations of the various conductor tubes 34, oriented casings 28,borehole casings 44, orienting mechanisms 42/52, and/or other componentsmay be adjusted according to the parameters of a given application.

Additionally, the processes employed may be adjusted according to theenvironment and/or parameters of a given well application. For example,various techniques may be used for drilling hole 36 and boreholes 32.Similarly, a variety of equipment and techniques may be employed forperforming the cementing operations both within hole 36 and alongboreholes 32. A number of other and/or additional components may be usedto facilitate drilling, cementing, testing, and/or productionoperations. Many types of configurations also may be used for modules 48to facilitate assembly of specific sequential modules which ensure thatinternal oriented casings 28 provide the proper predetermined exit angleand azimuthal orientation so as to enable formation of multiplenon-interfering boreholes and associated borehole casings.

Although a few embodiments of the disclosure have been described indetail above, those of ordinary skill in the art will readily appreciatethat many modifications are possible without materially departing fromthe teachings of this disclosure. Accordingly, such modifications areintended to be included within the scope of this disclosure as definedin the claims.

What is claimed is:
 1. A method for orienting casing strings,comprising: drilling a hole in a seabed; positioning a conductor tubeinto the hole; arranging a plurality of oriented casings in theconductor tube via modules which are aligned to position the orientedcasings so as to extend in a desired orientation; operating a drillstring through each orienting casing to form a borehole extendingbeneath the conductor tube along the desired orientation; and placingcasing along each borehole.
 2. The method as recited in claim 1, furthercomprising performing a cementing operation through an oriented casingof the plurality of oriented casings in the conductor tube prior toforming the boreholes beneath the conductor tube.
 3. The method asrecited in claim 2, wherein cementing comprises pumping cement down oneoriented casing of the plurality of oriented casings.
 4. The method asrecited in claim 3, further comprising providing a check valve in eachoriented casing to block upflow of cement into the plurality of orientedcasings during cementing.
 5. The method as recited in claim 1, whereindeploying the plurality of oriented casings comprises deploying twooriented casings in the conductor tube.
 6. The method as recited inclaim 1, wherein deploying the two oriented casings comprises deployingthe two oriented casings so as to extend into the conductor tube from adual wellhead.
 7. The method as recited in claim 1, wherein deployingthe two oriented casings comprises deploying the two oriented casings soas to extend into the conductor tube from a well bay.
 8. The method asrecited in claim 6, further comprising locating a plurality of the dualwellheads on a platform; and using pairs of the oriented casings foreach wellhead so as to provide unique orientations relative to theorientations of other pairs of oriented casings.
 9. The method asrecited in claim 1, further comprising aligning the modules viaalignment pins and corresponding alignment openings in adjacent modules.10. A system for orienting casing strings, comprising: a platformcooperating with a plurality of conductor tubes extending beneath aplatform to a seabed location, each conductor tube having a plurality oforiented casings which are arranged to provide a desired exit angle andazimuthal orientation, the plurality of oriented casings in theplurality of conductor tubes being arranged to facilitate formation ofboreholes extending from the pluralities of oriented casings; and aplurality of borehole casings placed in the boreholes so each boreholecasing extends from a corresponding oriented casing of the pluralitiesof oriented casings without interference from other boreholes orborehole casings.
 11. The system as recited in claim 10, wherein theplurality of oriented casings in each conductor tube comprises twooriented casings.
 12. The system as recited in claim 10, wherein theplurality of oriented casings in each conductor tube comprises checkvalves to facilitate cementing operations.
 13. The system as recited inclaim 10, wherein the borehole casings are cemented in the correspondingboreholes.
 14. The system as recited in claim 10, wherein the pluralityof oriented casings is constructed via an assembly of sequential,oriented modules.
 15. A method, comprising: placing a plurality ofconductor tubes into a seabed in conjunction with a platform; arranginga plurality of oriented casings in each conductor tube; using theorientation of each oriented casing to direct a corresponding drillingof a borehole and placement of a borehole casing in the borehole withoutinterfering with other boreholes and borehole casings associated withother oriented casings.
 16. The method as recited in claim 15, furthercomprising assembling the plurality of oriented casings as a series ofmodules arranged to establish the desired exit angle and azimuthalorientation for each plurality of oriented casings.
 17. The method asrecited in claim 15, further comprising performing a cementing operationthrough at least one of the oriented casings.
 18. The method as recitedin claim 17, further comprising placing check valves at lower ends ofthe oriented casings.
 19. The method as recited in claim 15, furthercomprising cementing each borehole casing in its corresponding borehole.20. The method as recited in claim 16, further comprising usingalignment features to couple together a desired sequence of modulescontaining sections of the oriented casings.